Field of the Invention
This disclosure relates to an organic light emitting diode. More particularly, the disclosure relates to an organic light emitting diode which can decrease driving voltage and improve lifetime by having an n type-charge generation layer (n-CGL) or electron transporting layer that is capable of injecting more electrons.
Discussion of the Related Art
In recent years, as the demand for flat panel displays is growing, organic light-emitting diode (OLED) devices are drawing attention. An OLED is a device that uses organic materials to convert electrical energy into light energy, and includes a layer of organic materials capable of emitting light, disposed between an anode and a cathode. OLEDs may form a variety of structures. Among those OLEDs, research on tandem organic light-emitting diodes with a plurality of emissive layers stacked is underway.
A tandem organic light-emitting diode is formed of a plurality of light-emitting parts, each having a hole injection layer, a hole transporting layer, an emissive layer, an electron transporting layer, and an electron injection layer stacked between an anode and a cathode. An n-type charge generation layer and a p-type charge generation layer are formed between each of the light-emitting parts of the tandem organic light-emitting diode. As electric charges are generated between the n-type charge generation layer and the p-type charge generation layer, electrons flow to the electron injection layer adjacent to the n-type charge generation layer, and holes are transported to the hole injection layer adjacent to the n-type charge generation layer. In this case, device efficiency depends on the interface characteristics and the difference in the energy level between the p-type charge generation layer and the n-type charge generation layer, and the interface characteristics and the difference in the energy level between the n-type charge generation layer and a doped alkali metal.
As the difference in energy level between the n-type charge generation layer and the p-type charge generation layer becomes larger, more charges are generated at the interface of the hole injection layer adjacent to the p-type charge generation layer, making electron injection into the n-type charge generation layer difficult.
Moreover, in the case of an n-type charge generation layer doped with an alkali metal, the alkali metal diffuses into the p-type charge generation layer, causing leakage current. The leakage current decreases the lifetime of the device.
A related art example of a compound for an organic photoelectronic device, an organic light-emitting diode including the same, and a display including the organic light emitting diode is provided in Korean Laid-Open Patent No. 2013-0079237.